By region impact of escaped farmed salmon on wild salmon stocks in Norway

Regional impact of escaped farm salmon on wild salmon populations in Norway. – NINA Report 622. 40 pp.
This report describes a regional, map-based presentation of changes in wild populations of Atlantic salmon (Salmo salar) caused by escaped, farm salmon during 1989-2009. The maps illustrate the results of model simulations which use as input mean values of estimates of the proportions of escaped farm salmon in the spawning populations and the reproductive success of farm salmon in controlled natural and semi-natural settings. The model predicts the proportions of the recruits after each spawning that have a wild salmon background, a farm salmon background, or a mix of the two. We have also estimated changes in the wild salmon populations in future salmon generations until year 2100, basing the model simulations on different scenarios for the proportions of farm salmon in future spawning populations: either as observed during the last ten years, or as a fixed percentage at 0 %, 5 % or 10 %. The results of our modeling show that by 2009, strong negative changes have occurred in many regions in Norway, and particularly so in the county of Hordaland, and that in the long run, large changes will take place in all regions if proportions of escaped farm salmon stay at the same levels as during the last ten years. Only one scenario, 0 % escaped farm salmon in the spawning populations, results in positive changes in all regions. For several regions it is urgent that this 0- scenario is realised.
Ola H. Diserud, Peder Fiske and Kjetil Hindar, Norwegian Institute for Nature Research (NINA).

Map of Norway showing the spawning population of salmon in Norway after spawning in 2009 and projections based on report findings. The color scale
indicates % share estimated spawning fish with wild salmon background.